Huh, how about that. I thought mistakenly that they had all the episodes from the beginning, but instead they only store ep 1, and eps 12-16.
I guess they don't expect complete newcomers to watch the show from the beginning on their site, so they only keep the 5 most recent episodes.
If you use this address:
http://www.nbc.com/Video/rewind/full_episodes/heroes.shtml?show=heroes01 and replace the "01" at the end with "12" - "16", you should be able to get those episodes playing.
And yes, Mohinder is a big dumb dumb head. It's not like he can help it though, since he's basically operating without any information other than what he's given. And most of what he's being given is false, anyway (at least by Sylar). I don't think he'd even seen Sylar's face before he went to the liquid-guy's apartment. It'd be child's play for Sylar, with his super-memory and who knows what other powers, to pull the wool over Mohinder's eyes.
And for Peter's powers, I think he can only use one or two powers at a time, otherwise he'd be invisible while flying around and such.
Edit: Maybe Peter's powers COME FROM HIS HAIR, lol. Naw, in all seriousness, I think they want him to be the brooding emo type to his brother's buttoned down scandalous politician. You have to admit, the hair contributes to about half of that image.